Commonly Used Terms in Oil & Gas Drilling

Absorber Capacity – The maximum volume of natural gas that can be processed through an absorber at a specified absorption oil rate, temperature, and pressure without exceeding pressure drop or any other operating limitation.

Absorption Oil – A hydrocarbon liquid used to absorb and recover components from natural gas before being processed.

Annulus – The space around a pipe in a well bore, also referred to as the annular space.

Api County Code – An indicator developed by the American Petroleum Institute (API) to identify areas such as counties and other subdivision areas identified within state boundaries. Defined by API Bulletin D12A, as amended. This code becomes a part of the API Well Number.

Api State Code – The indicator assigned to a state, as defined in API Bulletin D12A, as amended. This code is a part of the API Well Number

Api Well Number – A well identifier assigned as defined in API (American Petroleum Institute) Bulletin D12A, as amended. The API Well numbers are assigned by the appropriate state or federal regulatory agency.

Appraisal Well – A well drilled as part of an appraisal drilling program which is carried out to determine the physical extent, reserves and likely production rate of a field.

Barrel – A measure of volume for petroleum products in the U.S. Each barrel is the equivalent of 42 U.S. gallons.

Blow-down – Condensate and gas is produced simultaneously from the outset of production.

Blow-out – When well pressure exceeds the ability of the wellhead valves to control it. Oil and gas “blow wild” at the surface.

Blow-out Preventers (BOP’s) – High pressure wellhead valves that are designed to shut off the uncontrolled flow of hydrocarbons.

Borehole – The hole drilled by the drill bit

Bradenhead – A casinghead.

Bottomhole – The lowest or deepest part of a well.

Brine – Water that contains quantities of salt dissolved in it, particularly sodium chloride; salt water.

Casing – A steel pipe placed in an oil or gas well to prevent the wall of the hole from caving in, or to prevent the movement of fluids from one formation to another and aid on well control.

Casing string – The steel tubing that lines a well once it has been drilled, formed from sections of steel tubing screwed together.

Cellar – A pit in the ground to provide additional height between the rig floor and the well head.

Cement – A powder consisting of alumina, silica, lime and other substances that hardens when mixed with water. Used extensively in the oil industry to bond casing to the walls of the wellbore.

Central Estimate – A range of exploration drilling scenarios from which the following activity levels, based on recent historical experience, are adopted as the central estimates.

Christmas Tree – The assembly of fittings and valves on the top of the casing which control the production rate of oil.

Commercial Field – An oil and/or gas field judged to be capable of producing enough net income to make it worth developing.

Company man – An operating company employee who supervises the well or drilling site operations. Also referred to as a company hand or operator’s representative.

Completion – The installation of permanent wellhead equipment for the production of oil and natural gas.

Condensate – Hydrocarbons which are in the gaseous state under reservoir conditions and which become liquid when temperature or pressure is reduced. A mixture of pentanes and higher hydrocarbons.

Coring – Taking rock samples from a well with a special tool referred to as a core barrel.

Crane Barge – A large barge, capable of lifting heavy equipment onto offshore platforms. Also known as a derrick barge.

Crown Block – The set of pulleys or sheaves at the top of a mast on a rig.

Crude Oil – Liquid petroleum as it comes out of the ground as distinguished from refined oils manufactured out of it.

Cubic Foot – A standard unit used to measure quantity of gas (at atmospheric pressure); 1 cubic foot = 0.0283 cubic meters.

Cuttings – Rock chips cut from the formation by the drill bit, and brought to the surface with the mud. Used by geologists to obtain formation data.

Derrick – A large load-bearing structure, usually made of bolted construction. In drilling a standard derrick has four legs standing at the corners of the substructure, reaching to the crown block. The substructure consists of heavy beams used to elevate the derrick and provide space to install blowout preventers, casings and other materials.

Development Phase – The phase in which a proven oil or gas field is brought into production by drilling production (development) wells.

Doghouse – A small enclosure on the rig floor used as an office or a storehouse for small objects. Also, any small building used as an office or for storage.

Downhole – Term used pertaining to the wellbore

Drilling – The using of a rig and crew for the drilling, suspension, completion, production testing, capping, plugging and abandoning, deepening, plugging back, sidetracking, redrilling or reconditioning of a well (except routine cleanout and pump or rod pulling operations) or the converting of a well to a source, injection, observation, or producing well, and including stratigraphic tests. Also includes any related environmental studies. Associated costs include completion costs but do not include equipping costs

Drilling Rig – A drilling unit that is not permanently fixed to the seabed, e.g. a drillship, a semi-submersible or a jack-up unit. Also means the derrick and its associated machinery.

Dry Gas – Natural gas composed mainly of methane with only minor amounts of ethane, propane and butane and little or no heavier hydrocarbons in the gasoline range.

Dry Hole – A well proven to be non-productive.

E&A – Abbreviation for exploration and appraisal.

E&P – Abbreviation for exploration and production.

Enhanced Oil Recovery – A process whereby oil is recovered other than by the natural pressure in a reservoir.

Exploration Drilling – Drilling carried out to determine whether hydrocarbons are present in a particular area or structure.

Exploration Phase – The phase of operations which covers the search for oil or gas by carrying out detailed geological and geophysical surveys followed up where appropriate by exploratory drilling.

Exploration Well – A well drilled in an unproven area. Also known as a wildcat well.

Farm In – When a company acquires an interest in a block by taking over all or part of the financial commitment for drilling an exploration well.

Field – A geographical area under which an oil or gas reservoir lies.

Fishing – Retrieving objects from the borehole, such as a broken drillstring, or tools.

Formation Pressure – The pressure at the bottom of a well when shut in at the wellhead.

Formation Water – Salt water underlying gas and oil in the formation.

Frac Fluid – A fluid used in the fracturing process, Under extreme high hydraulic pressure, frac fluids (which can include distillate, diesel fuel, crude oil, dilute hydrochloric acid, water or kerosene) are pumped downward through production tubing or the drill pipe.

Fracing, or “Fracking” – See Hydraulic Fracturing.

G/C – Gas Condensate

Gas Field – A field containing natural gas but no oil.

Gas Injection – The process whereby separated associated gas is pumped back into a reservoir for conservation purposes or to maintain reservoir pressure.

Gas/Oil Ratio – The volume of gas at atmospheric pressure produced per unit of oil produced.

Geographic Information Systems (GIS) – A computer system capable of assembling, storing, manipulating, and displaying geographically referenced information

Geronimo Line – An escape line that provides a rapid escape path for the derrickman if needed due to well conditions or mechanical failure.

Horizontal Drilling – A deviation of the borehole from vertical so that the borehole penetrates a productive formation in a manner parallel to the formation.

Hydraulic Fracturing (“Fracking”) – The process in which a specially blended liquid is pumped into a well and into a formation under high pressure, which causes the formation to break open.

Hydrocarbon – A compound containing only the elements hydrogen and carbon. May exist as a solid, a liquid or a gas. The term is mainly used in a catch-all sense for oil, gas and condensate.

Injection Well – A well used for pumping gas into the reservoir.

Jacket – The lower section (legs) of an offshore platform.

Kick – When the formation pressure exceeds the pressure exerted by the mud column.

Kill – In drilling, to control a kick by taking preventative measures. In production, to stop a well from producing oil and gas in order to recondition the well.

Liquefied Natural Gas (LNG) – Oilfield or naturally occurring gas, chiefly methane, liquefied for transportation.

Liquefied Petroleum Gas (LPG) – Light hydrocarbon material, gaseous at atmospheric temperature and pressure, held in the liquid state by pressure to facilitate storage, transport and handling. Commercial liquefied gas consists essentially of either propane or butane, or mixtures thereof.

mboe – Million Barrels Oil Equivalent

Mechanical Integrity Test (MIT) – The act of setting a packer or retrievable bridge plug above the perforations in a wellbore and applying pressure to the annulus in order to ensure soundness of the casing.

Metric Ton – Equivalent to 1000 kilos, 2204.61 lbs.; 7.5 barrels.

mmcfd – Millions of cubic feet per day (of gas).

Monkeyboard – A working platform for the derrickhand in the derrick or mast.

Moonpool – An aperture in the center of a drillship or semi-submersible drilling rig, through which drilling and diving operations can be conducted.

MOU/MOA – Memorandums Of Understanding/Agreement

Mousehole – Shallow bores under the rig floor, usually lined with pipe, in which joints of drill pipe are temporarily suspended for later connection to the drill string.

Mud – Liquid that is circulated through the wellbore in rotary drilling and workover operations.

Mud Pit – An open pit dug into the ground to hold drilling fluid or waste materials discarded after mud drilling treatment.

Mud Tank – An open tank generally made of steel plate through which the drilling mud is cycled to remove sand and other sediments.

Natural Gas – Gas, occurring naturally, and often found in association with crude petroleum.

O&G – Oil & Gas

Oil – A mixture of liquid hydrocarbons of different molecular weights.

Oil Field – A geographical area under which an oil reservoir lies.

Oil In Place – An estimated measure of the total amount of oil contained in a reservoir, and, as such, a higher figure than the estimated recoverable reserves of oil.

Operator – The company that has legal authority to drill wells and undertake the production of hydrocarbons that are found. The Operator is often part of a consortium and acts on behalf of this consortium.

Payzone – Rock in which oil and gas are found in exploitable quantities.

Perforation – A hole made in the casing, cement and formation through which formation fluids enter a wellbore.

Perforating Gun – A device fitted with shaped charges or “bullets” that is lowered to the desired depth in a well and fired to create penetrating holes in casing, cement and formation.

Permeability – The property of a formation which quantifies the flow of a fluid through the pore spaces and into the wellbore.

Petroleum – A generic name for hydrocarbons, including crude oil, natural gas liquids, natural gas and their products.

Porosity – The percentage of void in a porous rock compared to the solid formation.

Possible Reserves – Those reserves which at present cannot be regarded as ‘probable’ but are estimated to have a significant but less than 50% chance of being technically and economically producible.

Primary Recovery – Recovery of oil or gas from a reservoir purely by using the natural pressure in the reservoir to force the oil or gas out.

Probable Reserves – Those reserves which are not yet proven but which are estimated to have a better than 50% chance of being technically and economically producible.

Proven Field – An oil and/or gas field whose physical extent and estimated reserves have been determined.

Proven Reserves – Those reserves which on the available evidence are virtually certain to be technically and economically producible, such as those having a better than 90% chance of being produced.

Pusher – See Toolpusher.

Rathole – A shallow, small-diameter, auxiliary hole alongside the main borehole, drilled at an angle to the main hole; after core drilling is completed, the rathole is reamed out and the larger-size hole is advanced, usually by some noncoring method.

Recomplete – An operation involving any of the following:

  • Deepening from one zone to another
  • Completing wells in additional zones
  • Plugging back from one zone to another
  • Sidetracking to change the location of the bottom of the well
  • Conversion of a service well to an oil or gas well in a different zone
  • Conversion of an oil or gas well to a service well in a different zone

Recovery Factor – That proportion of the oil and/gas in a reservoir that can be removed using currently available techniques.

Reservoir – The underground formation where oil and gas has accumulated. It consists of a porous rock to hold the oil or gas, and a cap rock that prevents its escape.

Rig Manager – See Toolpusher.

Riser – In drilling, the pipe between a seabed BOP and floating drilling rig. In production, the section of pipework that joins a seabed wellhead to the Christmas tree.

Roughneck – A worker on a drilling or workover rig whose primary work station is the rig floor. Also referred to as floorhand, floorman or rig crew member.

Roustabout – Drill crew members who handle the loading and unloading of equipment and assist in general operations around the rig.

Secondary Recovery – Recovery of oil or gas from a reservoir by artificially maintaining or enhancing the reservoir pressure by injecting gas, water or other substances into the reservoir rock.

Shut In Well – A well which is capable, but not presently producing.

Shutdown – A production hiatus where the platform ceases to produce during maintenance work.

SI/TA – Shut In/Temporarily Abandoned

Sidetrack – A wellbore segment extending from a wellbore intersection along a wellbore path to a different wellbore bottomhole from any previously existing wellbore bottomholes.

Sidetracking – The well activity of drilling a new wellbore segment from a wellbore intersection to a new wellbore bottomhole or target.

Spud-in – The operation of drilling the first part of a new well.

Stimulation – A variety of operations performed on a well to improve productivity.

Surface Location – The location of a well; its measurement point

Surface Reclamation – A restoration of the surface for productivity.

Suspended Well – A well that has been temporarily capped off.

tcf – Trillion Cubic Feet (of gas)

Tongs – Large wrenches used for turning when making up or breaking out drill pipe, casing, tubing or other pipe. Also called casing tongs or rotary tongs.

Toolpusher – An employee of the drilling contractor who is in charge of the drilling crew and rig. Also referred to as a rig superintendent, drilling foreman or rig supervisor.

Topsides – The superstructure of a platform.

Underground Injection Control (UIC) – A program required in each state by a provision of the Safe Drinking Water Act (SDWA) for the regulation of Injection Wells, including a permit system. An applicant must demonstrate that the well has no reasonable chance of adversely affecting the quality of an underground source of drinking water before a permit is issued.

V-Door – An opening at floor level in a side of a derrick or mast, opposite the draw works and used as an entry to bring in drill pipe, casing and other tools from the pipe rack.

Well Log – A record of geological formation penetrated during drilling, including technical details of the operation.

Wellbore – A borehole; the hole drilled by the bit.

Wildcat Well – A well drilled in an unproven area. Also known as an exploration well.

Workover – Remedial work to the equipment within a well, the well pipework, or relating to attempts to increase the rate of flow.

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